function sleep(n){
	var now = new Date()
	var exitTime = now.getTime() + n
	while(true){
		now = new Date()
		if(now.getTime() > exitTime){
			return
		}
	}
}

onmessage = function(event){
	var num = event.data
	console.log("接收到主线程发来的数据")
	sleep(600)
	var result = Math.sqrt(num)
	postMessage(result)
}